Security readout for executives and security teams
Plain-English summary
CVE-2026-2779 is a critical Mozilla vulnerability in the Networking: JAR component, fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8. Mozilla describes incorrect boundary conditions, a memory-safety class issue, with potential full confidentiality, integrity, and availability impact. No provided source indicates active exploitation.
Executive priority
Patch promptly across browsers and mail clients. The business risk is high because the issue is critical, remotely reachable by CVSS assessment, and affects widely deployed user applications. There is no sourced evidence of active exploitation, but delayed patching leaves a large and attractive attack surface.
Technical view
The CVE describes CWE-119 incorrect boundary conditions in Mozilla’s Networking: JAR component. CVSS 3.1 is 9.8: network exploitable, low complexity, no privileges, no user interaction, with high CIA impact. Public detail is limited; the advisory set identifies fixed releases but does not provide exploitation mechanics in the supplied bundle.
Likely exposure
Organizations using Firefox, Firefox ESR, or Thunderbird below the fixed release lines may be exposed. The source bundle names fixed versions, not exact vulnerable ranges. Exposure is highest where Mozilla clients are internet-facing through normal browsing or mail handling, and where update compliance is weak.
Exploitation context
The CVSS vector indicates possible remote, unauthenticated exploitation without user interaction, but the supplied sources do not confirm exploitation in the wild. It is not listed as KEV in the provided data. Treat as urgent because browser and mail-client memory issues can have broad enterprise reach.
Researcher notes
Public technical detail is sparse. The Bugzilla and MFSA references should be monitored for clarifications, affected range precision, and any follow-up advisories. Avoid assuming exploitability details beyond the CVSS vector and Mozilla’s component description.
Mitigation direction
- Update Firefox to 148 or later, based on Mozilla advisory guidance.
- Update Firefox ESR to 140.8 or later.
- Update Thunderbird to 148 or later, or 140.8 or later for ESR line.
- Check Mozilla advisories for platform-specific release notes and any revised guidance.
- Prioritize managed endpoints, VDI images, and mail-client installations.
Validation and detection
- Inventory Firefox, Firefox ESR, and Thunderbird versions across managed assets.
- Confirm installed versions meet or exceed the fixed releases named by Mozilla.
- Review endpoint management reports for update failures or unmanaged installations.
- Monitor Mozilla advisory pages for changes to affected ranges or remediation guidance.
- Check vulnerability scanner plugins against Mozilla’s fixed-version information.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-119: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-2779 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.mozilla.org/show_bug.cgi?id=1164141CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-13/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-15/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-16/CVE reference
- https://www.mozilla.org/security/advisories/mfsa2026-17/CVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Restriction of Operations within the Bounds of a Memory Buffer
Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.